S. Schwartz et al., Numerical model of the effect of serpentinites on the exhumation of eclogitic rocks: insights from the Monviso ophiolitic massif (Western Alps), TECTONOPHYS, 342(1-2), 2001, pp. 193-206
The intimate association of serpentinite melange with eclogites worldwide s
uggests that serpentinites may have played an important role in the exhumat
ion of eclogites. Serpentinites may have formed by fluid percolation in the
mantle wedge or by underplating of oceanic serpentinites, We have tested n
umerically the role of serpentinites in the exhumation of eclogites using p
hysical parameters obtained in the Monviso massif of the Western Alps. Our
calculation shows that the buoyancy of serpentinized peridotites in dense a
nhydrous peridotites may contribute to the exhumation of eclogitic blocks.
Small eclogitic blocks (< km(3)) may be exhumed in completely hydrated mant
le wedge, but it is not common considering the absence of totally serpentin
ized peridotites in mantle wedges. The exhumation of large eclogitic blocks
(> 50 km(3)) requires a viscosity of the serpentinite wedge to be between
10(20)and 10(21) Pa and a density difference between the serpentinite wedge
and the surrounding mantle on the order of 100-400 kg m(- 3) This conditio
n is satisfied by only partially hydrated peridotites containing 10-50% ser
pentinites, Such serpentinized peridotites are expected to form at a depth
ranging from 20 to 60 km in subduction zones by dehydration of subducting p
lates. Our conclusion is supported by the common occurrences of partially h
ydrated peridotites in close association with high-pressure to ultra-high-p
ressure metamorphic rocks. (C) 2001 Elsevier Science B.V. All rights reserv
ed.